Commit 96ba44c6 authored by Jaco Kroon's avatar Jaco Kroon Committed by David S. Miller
Browse files

net/pppoe: make number of hash bits configurable 



When running large numbers of pppoe connections, a bucket size of 16 may
be too small and 256 may be more appropriate.  This sacrifices some RAM
but should result in faster processing of incoming PPPoE frames.

On our systems we run upwards of 150 PPPoE connections at any point in
time, and we suspect we're starting to see the effects of this small
number of buckets.

The legal values according to pppoe.c is anything that when 8 is divided
by that results in a modulo of 0, ie, 1, 2, 4 and 8.

The size of the per-underlying-interface structure is:

sizeof(rwlock_t) + sizeof(pppox_sock*) * PPPOE_HASH_SIZE.

Assuming a 64-bit pointer this will result in just over a 2KiB structure
for PPPOE_HASH_BITS=8, which will likely result in a 4KiB allocation,
which for us at least is acceptable.

Not sure what the minimum allocation size is, and thus if values of 1
and 2 truly make sense.  Default results in historic sizing and
behaviour.

Signed-off-by: default avatarJaco Kroon <jaco@uls.co.za>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c83ae452

drivers/net/ppp/Kconfig

+34 −0
Original line number Diff line number Diff line
@@ -129,6 +129,40 @@ config PPPOE 
	  which contains instruction on how to use this driver (under

	  the heading "Kernel mode PPPoE").



choice

	prompt "Number of PPPoE hash bits"

	default PPPOE_HASH_BITS_4

	depends on PPPOE

	help

		Select the number of bits used for hashing PPPoE interfaces.



		Larger sizes reduces the risk of hash collisions at the cost

		of slightly increased memory usage.



		This hash table is on a per outer ethernet interface.



config PPPOE_HASH_BITS_2

	bool "1 bit (2 buckets)"



config PPPOE_HASH_BITS_2

	bool "2 bits (4 buckets)"



config PPPOE_HASH_BITS_4

	bool "4 bits (16 buckets)"



config PPPOE_HASH_BITS_8

	bool "8 bits (256 buckets)"



endchoice



config PPPOE_HASH_BITS

	int

	default 1 if PPPOE_HASH_BITS_1

	default 2 if PPPOE_HASH_BITS_2

	default 4 if PPPOE_HASH_BITS_4

	default 8 if PPPOE_HASH_BITS_8

	default 4



config PPTP

	tristate "PPP over IPv4 (PPTP)"

	depends on PPP && NET_IPGRE_DEMUX

drivers/net/ppp/pppoe.c

+1 −1
Original line number Diff line number Diff line
@@ -80,7 +80,7 @@ 


#include <linux/uaccess.h>



#define PPPOE_HASH_BITS 4

#define PPPOE_HASH_BITS CONFIG_PPPOE_HASH_BITS

#define PPPOE_HASH_SIZE (1 << PPPOE_HASH_BITS)

#define PPPOE_HASH_MASK	(PPPOE_HASH_SIZE - 1)